Atlantic salmon and sea trout caught at sea or in UK rivers are known to be at risk of being infected with a parasitic worm called anisakis.

Parasites in fish, particularly anisakis, can cause serious health problems if eaten alive, including acute gastrointestinal symptoms and severe allergic reaction.

The Food Standards Agency has issued the following advice for anyone eating wild Atlantic salmon or sea trout privately caught at sea or from UK rivers:

Remove the guts

Remove the guts and then visually inspect the fish body cavity and muscle walls to detect and remove all visible parasites.

Anisakis worms may be seen on the surfaces of tissues around the gut. Worms are colourless and normally coiled like a spring within a cyst. Worms range in size from 5mm-20mm.

In most cases, especially in salmon, they may also be found within the muscles, especially in those that surround the body cavity and the anus. It's important to check the muscle surrounding the anus, particularly if the fish have red and swollen vents.

Freeze before eating

If wild fish are to be eaten raw or lightly cooked, all parts should be frozen at -15C or colder for at least four days in a domestic freezer. This will ensure that any undetected parasites are destroyed.

This freezing advice also relates to wild caught fish that are to be cold smoked or eaten after marinating or salting.

Cook thoroughly

Where wild caught fish are to be hot smoked (at a core temperature above 60C), the flesh of the fish should be steaming hot throughout after smoking and generally have a flaky texture. This cooking process will kill any parasites present, and make the fish safe to eat without freezing first.

Where it is not possible to freeze the fish properly, cook the fish at a temperature of 70C for two minutes to kill any parasites present. 

Shop bought fish

Controls are in place to ensure that the presence of parasites in fishery products purchased in a shop is kept to a minimum.

Food businesses that sell fishery products are required to visually examine the fish to check for parasites and they must not sell the products if they are obviously contaminated with parasites.   In addition, unless the fishery product meets exemption requirements, all fishery products that are to be consumed raw or lightly cooked (e.g. sushi), marinated, salted or subjected to other treatments are required to undergo a freezing treatment to kill any viable parasites.